【新人求助】关于回收站的一个问题

已知回收站图标0.png和1.png
[MeasureIsFull]
Measure=CALC
Formula=MeasureBinNum>0
[MeasureIsFullInverted]
Measure=CALC
Formula=MeasureIsFull+2
[BinIcon]
Meter=IMAGE
MeasureName=MeasureIsFull
ImageName=%1.png
X=-9
Y=0
W=106
H=106
AntiAlias=1
其中
[MeasureIsFullInverted]
Measure=CALC
Formula=MeasureIsFull+2
什么意思，
为什么不直接写
[MeasureIsFull]
Measure=CALC
Formula=MeasureBinNum>0?1:0